1. Field
This disclosure relates to a composition for a rigid polyurethane foam and a rigid polyurethane foam produced using the same. This disclosure relates more particularly, to a rigid polyurethane foam with improved insulation efficiency, fabricated using an eco-friendly additive.
2. Description of the Related Art
In order to utilize a material as thermal insulation, it is desirable that the material have a low density and display buffer (or cushioning) properties to stimuli such as, for example, sound, impact and/or shock. Polyurethane foams are used as thermal insulation materials because of their low density and because of their ability to serve as a barrier against the propagation of sound or heat and to serve as a buffer against impact and/or shock. Polyurethane foams can be used as light weight construction materials, buffer materials, and the like, either alone or in combination with other materials. In particular, a rigid polyurethane foam having the lowest thermal conductivity among commonly available insulation materials exhibits excellent thermal insulation properties, and therefore, is broadly employed in fabrication of various thermal insulation materials for refrigerators, construction applications, and the like, and/or in the manufacture of electronics, where a high insulation efficiency is desirable.
Recently, in order to improve insulation efficiency (often referred to as “k-factor”) of such rigid polyurethane foam, a great deal of studies and investigations have been conducted. The thermal conductivity of the polyurethane foam generally includes about 50 to about 65% of thermal conductivity due to gas conductivity, about 15 to about 20% of thermal conductivity due to conductivity of the solid components (hereinafter solids conductivity) and about 20 to about 30% of thermal conductivity due to conductivity by radiation. Attempts to decrease the size of discrete cells in a polyurethane foam have been carried out in order to reduce the thermal conductivity of the foam. It is known that such results are achieved by improvement in the efficiency of thermal insulation owing to the inhibition of heat transfer via radiation, thereby leading to a reduction in thermal conductivity. In order to decrease the size of the discrete cells in the polyurethane foam, a proposal has been made to increase the amount of nucleating agent to produce a larger number of cells that are of a smaller size than a comparative foam that uses a smaller amount of the same nucleating agent. As a result, the size of each cell is decreased thereby enhancing insulation efficiency. Some of the nucleating agents and blowing agents used for the production of polyurethane forms are not environmentally friendly. It is therefore desirable to improve the insulating efficiency of a rigid polyurethane foam by using an eco-friendly additive.